If your gas boiler stops working in cold weather, it is likely to be caused by a frozen condensate pipe. If you have a Glow-worm boiler, it should show an F1 or F4 fault code if this has happened.
Condensate pipes usually freeze at the most exposed point, outside your property.
It’s fairly easy to thaw the pipe and fix the problem – simply pour hot (not boiling) water over it. You might need to do this several times.
Take care when doing this – if the water freezes on the ground it could cause a slip hazard.
To check whether the pipe has thawed, press the reset button on the front of the boiler, or turn it back on if you had turned it off. If it starts, the pipe has thawed. If it doesn’t, try pouring more hot water on the pipe.